<?php
$setup = $this;
$installer = new Mage_Eav_Model_Entity_Setup('core_setup');
$setup->startSetup();

$installer->addAttribute('catalog_category', 'static_url', array(
'input' => 'text',
'type' => 'text',
'label' => 'Static Url',
'visible' => true,
'required' => false,
'visible_on_front' => false,
'searchable' => false,
'used_in_product_listing' => false,
));
$setup->endSetup();